This invention relates to a process for treating (e.g. repairing) inorganic building materials such as asbestos slates.
When asbestos slates which are used as roof tiles and the like are aged, these slates are exchanged for new ones, or repaired by removing earth and sand, moss, etc., deposited on or adhered to surfaces thereof, by blowing highly pressurized water against the surfaces or by brushing with a wire brush to completely remove aged portions, followed by coating again. According to the former exchanging method, it requires a great deal of labor and expense. On the other hand, according to the latter reparing method, there are many problems in that incomplete removal of the contaminants readily brings about peeling of coating in an early time due to weak adhesiveness, strength of asbestos slates is lowered by the use of highly pressurized water and brushing, floating of asbestos powder which is harmful for human bodies and generated by brushing aged surfaces of asbestos slates brings about problems on safety and environmental pollution.
In order to overcome some of these problems, Japanese Patent Unexamined Publication No. 59-173462 discloses a process for repairing asbestos slates comprising coating a polyisocyanate compound on surfaces of asbestos slates for impregnation, curing said compound, and coating a coating composition thereon. According to this process, the asbestos slates can be regenerated so as to have original strength and excellent durability, but there are many problems in that the range of molecular weight of polyisocyanate compound is very limited, the use of a solvent is essential in order to impregnate the polyisocyanate compound, which results in causing many problems on workability, safety, etc., and the process becomes elaborate and uneconomical due to the surface coating so as to provide weather resistance.